1. Field
The presently disclosed subject matter relates to a vehicle headlamp including a two-dimensional optical deflector.
2. Description of the Related Art
A prior art vehicle headlamp is constructed by a light source for emitting a light basic pattern (spotlight) and a two-dimensional optical deflector for reflecting the spotlight to ahead of a vehicle. The two-dimensional optical deflector includes a mirror for reflecting the spotlight from the light source, a movable frame surrounding the mirror for supporting the mirror, a first actuator for vibrating (rocking) the mirror with respect to an X-axis of the mirror, a support body surrounding the movable frame, and a second actuator for rocking the mirror through the movable frame with respect to a Y-axis of the mirror perpendicular to the X-axis. Thus, the two-dimensional rocking operation of the mirror is controlled to control a light distribution pattern (see: FIGS. 12, 13(a) and 13(b) of U.S. 2009/0046474A1 & JP 2009-48786A).
When an illumination area along a horizontal line and a vertical line ahead of the vehicle corresponding to the X-axis and Y-axis, respectively, of the mirror is raster-scanned with the spotlight by the two-dimensional optical deflector, a light distribution pattern which is relatively bright in the vicinity of a cut-off boundary line can be obtained. Note that the illumination area is set under the cut-off boundary line. In this case, the mirror is rocked with respect to the X-axis for a horizontal deflection at a high frequency by the first actuator, while the mirror is rocked with respect to the Y-axis for a vertical deflection at a low frequency by the second actuator. Therefore, the larger the distance from the two-dimensional optical deflector, the larger the density of scan lines depicted by the spotlight. As a result, regularity of illumination and better distant visibility may be obtained in the vicinity of the cut-off boundary line.
In the above-described prior art vehicle headlamp, however, since each of the scan lines in the vicinity of the cut-off boundary line would still be clearly observed as lines, irregularity of illumination would still occur in the vicinity of the cut-off boundary line.
Also, since the spotlight is scanned uniformly along the horizontal line, a bright center portion as required for the vehicle would not be realized.